Sliding component

ABSTRACT

Even when a fluid discharge for discharging high-pressure fluid (sealed fluid) to a high-pressure side of a sealing face is provided, the disclosed sliding component prevents precipitation, adhesion and accumulation of a deposition-causing substance through a dehydration condensation reaction between the high-pressure fluid and low-pressure fluid on the sealing face, and also prevents occurrence of cavitation which would otherwise take place in association with a sudden pressure drop due to a discharge of fluid. Disclosed is a pair of sliding components provided, on a high-pressure side of one of relatively sliding sealing faces thereof, with a fluid discharge for discharging fluid to a high-pressure fluid side, wherein a buffer groove for reducing penetration of low-pressure fluid toward the high-pressure fluid side is provided in the sealing face S on a low-pressure side of the fluid discharge.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application based on U.S. patentapplication Ser. No. 14/758,765, filed Jun. 30, 2015, which in turn, isa 371 of PCT/JP2013/084029, filed Dec. 19, 2013, the contents of whichare incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a sliding component suitable, forexample, for a mechanical seal, a bearing unit or other sliding part.Particularly, the present invention relates to a sliding component suchas a seal ring or bearing that requires both reduction in friction byinterposing fluid between sealing faces and prevention of leakage of thefluid from the sealing faces.

BACKGROUND ART

In a mechanical seal that is one example of such a sliding component,the performance thereof is evaluated based on leakage rate, wear rateand torque. In conventional technologies, a reduction in leakage, anextension in life and a reduction in torque are attained by optimizingthe sliding material and sealing face roughness of a mechanical seal toenhance the performance. However, due to a recent rise in the awarenessof environmental problems, further improvements in the performance ofmechanical seals are demanded, and technical developments beyond thebounds of the conventional technologies are increasingly neededaccordingly. The conventional technologies for mechanical seal includeone that achieves improved seal function at a sealing face by providing,as shown in FIG. 10, a sliding component 50 with spiral grooves 52 in asealing face 51 thereof and forcing sealed fluid, which would otherwiseleak to a low-pressure fluid side, back toward a high-pressure fluidside through the use of pumping action of the spiral grooves 52 (forexample, refer to Patent Citation 1).

CITATION LIST Patent Literature

Patent Citation 1: JP-A-61-82177 (U) (FIGS. 1 and 2)

SUMMARY OF INVENTION Technical Problem

According to the above-mentioned conventional technology, the sealingface 51 is provided on a high-pressure side with the spiral grooves 52angled to discharge fluid to the high-pressure fluid side by relativesliding with a counter sealing face, whereby the fluid is forced back tothe high-pressure fluid side under the viscous pump effect of the spiralgrooves 52 to prevent the leakage.

However, the present inventors' studies revealed that in this type ofmechanical seals, low-pressure fluid 53, for example, air penetrates tothe low-pressure fluid side of the sealing face under the a fluidpumping effect by sliding, and promotes a dehydration condensationreaction of high-pressure fluid, that is, sealed fluid existing aslubricating fluid on the sealing face, and that the resultingprecipitation, adhesion and accumulation of a deposition-causingsubstance on the sealing face lead to a deterioration in the sealingperformance of the sealing face.

The above-mentioned conventional technology also involves a problem inthat the lubrication of the sealing face is insufficient.

A first object of the present invention is to provide a slidingcomponent, which has is improved seal function at a sealing face thereofby preventing, even when the sliding component is provided with a fluiddischarge means for discharging high-pressure fluid (sealed fluid) to ahigh-pressure side of the sealing face, a deterioration in the sealingperformance of the sealing face based on prevention of precipitation,adhesion and accumulation of deposition-causing substance through a thedehydration condensation reaction on the sealing face between thehigh-pressure fluid and the low-pressure fluid and also the preventionof the occurrence of cavitation associated with a sudden pressure dropdue to a discharge of fluid.

A second object of the present invention is to provide a slidingcomponent configured to have a sealing face provided with improvedlubricity without reducing the negative pressure generating capacity ofa fluid discharge means.

Solution to Problem

{Principle}

The present invention is firstly to provide, in sliding componentsincluding a fluid discharge means provided on a high-pressure side of asealing face of at least one of the sliding components for dischargingfluid to a high-pressure fluid side, a buffer groove in the sliding faceon a low-pressure side of the fluid discharge means for reducingpenetration of low-pressure fluid toward the high-pressure fluid side.The buffer groove, which is provided in the sealing face on thelow-pressure side of the fluid discharge means, functions as a bufferfor the low-pressure fluid, which penetrates from the low-pressure fluidside onto the sealing face, against the high-pressure fluid, whereby thetime until the sealing face is filled with the low-pressure fluid can bedelayed to suppress the dehydration condensation reaction of thehigh-pressure fluid.

When the low-pressure fluid is air, for example, the low-pressure sideof the sealing face can be prevented from drying with air. Theprecipitation, adhesion and accumulation of a deposition-causingsubstance through the dehydration condensation reaction of thehigh-pressure fluid can be prevented accordingly.

The occurrence of cavitation associated with a sudden pressure drop dueto a discharge of fluid can be also prevented.

The present invention is secondly to provide, in sliding componentsincluding a fluid discharge means for discharging fluid to ahigh-pressure fluid side on a sealing face of one of the, a positivepressure generating mechanism on a high-pressure side of the sealingface and also a fluid discharge means for discharging fluid to thehigh-pressure side on a low-pressure side of the positive pressuregenerating mechanism, and also a pressure releasing groove between thepositive pressure generating mechanism and the fluid discharge means.

The positive pressure generating mechanism improves the lubricity bybroadening the space between the relatively sliding sealing facesthrough the generation of a positive pressure (dynamic pressure) andforming a liquid film between the sealing faces. The pressure releasinggroove, on the other hand, maintains the seal function between thesealing faces by releasing a positive pressure (dynamic pressure), whichhas been generated by the positive pressure generating mechanism on thehigh-pressure side, to the pressure of the fluid on the high-pressureside to prevent the fluid from flowing into the fluid discharge meansand the negative pressure generating capability of the fluid dischargemeans from being lessened.

{Means}

To attain the above-mentioned objects, a pair of sliding componentsaccording to the present invention firstly features that in the pair ofsliding components provided, on a high-pressure side of one ofrelatively sliding sealing faces thereof, with, wherein a buffer groovefor reducing penetration of low-pressure fluid toward the high-pressurefluid side is provided in the fluid discharge means.

According to this feature, the buffer groove provided in the sealingface on the low-pressure side of the fluid discharge means functions asa buffer for the low-pressure fluid, which penetrates from thelow-pressure fluid side onto the sealing face, against the high-pressurefluid, whereby the time until the sealing face is filled with thelow-pressure fluid can be delayed to suppress the dehydrationcondensation reaction of the high-pressure fluid.

When the low-pressure fluid is air, for example, the low-pressure sideof the sealing face can be prevented from drying with air. Theprecipitation, adhesion and accumulation of a deposition-causingsubstance through the dehydration condensation reaction of thehigh-pressure fluid can be prevented accordingly.

Even if a sudden pressure drop occurs due to a discharge of fluid by thefluid discharge means, the occurrence of cavitation can be preventedsince the sudden pressure drop is reduced by the fluid existing in thebuffer groove.

The sliding components of the present invention secondly features thatin the first feature, the buffer groove is preferably formed in asemicircular, rectangular or dovetail shape in cross-section.

The sliding components of the present invention thirdly features that inthe first or second feature, buffer groove has a width b set preferablyat 10 to 500 μm, more preferably at 50 to 200 μm.

The sliding components of the present invention fourthly features thatin the third feature, the buffer groove has a depth h set at 1 to 2times the width b.

According to these features, the capacity of the buffer groove can beincreased while securing the sealing face.

The sliding components of the present invention fifthly features that inany one of the first to fourth features, the fluid discharge meanscomprises a spiral groove.

According to this feature, despite the adoption, as the fluid dischargemeans, of the spiral groove associated with a potential sudden pressuredrop due to its high fluid discharge function (high sealing effect), theprecipitation, adhesion and accumulation of a deposition-causingsubstance through the dehydration condensation reaction of high-pressurefluid can be prevented and the occurrence of cavitation can be alsoprevented.

The sliding components of the present invention sixthly features that inany one of the first to fourth features, the fluid discharge meanscomprises a reverse Rayleigh step.

According to this feature, despite the adoption, as the fluid dischargemeans, of the reverse Rayleigh step associated with a potential suddenpressure drop due to its high fluid discharge function (high sealingeffect), the precipitation, adhesion and accumulation of adeposition-causing substance through the dehydration condensationreaction of high-pressure fluid can be prevented and the occurrence ofcavitation can be also prevented.

The sliding components of the present invention seventhly features thatin the fifth or sixth feature, the sealing face is provided, on thehigh-pressure side thereof, with a fluid circulation groove incommunication with the high-pressure fluid side in addition to thespiral groove or reverse Rayleigh step, and is also provided with apositive pressure generating mechanism in a part flanked by the fluidcirculation groove and the high-pressure fluid side; and the positivepressure generating mechanism is in communication with an inlet portionof the fluid circulation groove and is isolated from an outlet portionof the fluid circulation groove and the high-pressure side by a landportion.

According to this feature, despite the provision of the fluidcirculation groove, which plays a role of actively introducing anddischarging sealed fluid from the high-pressure fluid side onto and fromthe sealing face for preventing fluid and corrosion products and thelike contained therein from concentrating on the sealing face, inaddition to the spiral groove or reverse Rayleigh step associated with apotential sudden pressure reduction, the precipitation, adhesion andaccumulation of a deposition- causing substance through the dehydrationcondensation reaction of high-pressure fluid can be prevented and theoccurrence of cavitation can be also prevented.

A pair of sliding components according to the present invention eighthlyfeatures that in the pair of sliding components provided, on ahigh-pressure side of one of relatively sliding sealing faces thereof,with a fluid discharge means for discharging fluid to a high-pressurefluid side, wherein a positive pressure generating mechanism forgenerating a positive pressure is provided in the sealing face on ahigh-pressure side of the fluid discharge means such that the positivepressure generating mechanism is isolated from the high-pressure fluidside by a land portion; an annular pressure releasing groove providedbetween the fluid discharge means and the positive pressure generatingmechanism, the pressure releasing groove is connected to adischarge-side end of the fluid discharge means, and is separated fromthe positive pressure generating mechanism in a radial direction by aland part; and a radial groove provided to communicate the pressurereleasing groove and the high-pressure fluid side with each other, andthe radial groove is provided at a position where the radial groove isin contact with an upstream end of the positive pressure generatingmechanism.

According to this feature, the lubricity can be improved by broadeningthe space between the relatively sliding sealing faces by the positivepressure generating mechanism and forming a liquid film between thesealing faces, and the sealing performance between the sealing faces canbe also improved by releasing a positive pressure (dynamic pressure),which has been generated by the positive pressure generating mechanismon the high-pressure side, to the pressure of the fluid on thehigh-pressure side through the pressure releasing groove to prevent thefluid from flowing into the fluid discharge means and the negativepressure generating capability of the fluid discharge means from beinglessened.

The sliding components of the present invention ninthly features that inthe eighth feature, an even number of radial grooves are disposed in acircumferential direction, each adjacent ones of the radial grooves aredifferent from each other in the direction of inclination, or an inletof each radial groove in one group is inclined toward an upstream side,and an outlet of each radial groove in the other group is inclinedtoward a downstream side.

According to this feature, a gentle flow of fluid is produced in a deepgroove constituted by the pressure releasing groove and the radialgroove. Therefore, bubbles, impurities and the like are prevented fromstaying in the deep groove, fluid which is about to flow in toward thelow-pressure side can be surely released to the high-pressure fluid sideunder a pressure generated by the positive pressure generating mechanismon the high-pressure fluid side, and the sealing performance can be thusimproved.

The sliding component of the present invention tenthly features that inthe eighth or ninth feature, the sealing face is provided, on thelow-pressure side of the fluid discharge means, with a buffer groovethat reduces the penetration of low-pressure fluid toward thehigh-pressure fluid side.

According to this feature, despite the positive pressure generatingmechanism provided to improve the lubricity by broadening the spacebetween the sealing faces and forming a film of fluid between thesealing faces, and the provision of the pressure releasing groove whichplays a role of releasing fluid, said fluid being about to flow intoward the low-pressure side under a pressure generated by thehigh-pressure side positive pressure generating mechanism on thehigh-pressure fluid side, the precipitation, adhesion and accumulationof a deposition-causing substance through the dehydration condensationreaction of high-pressure fluid can be prevented and the occurrence ofcavitation can be also prevented.

Advantageous Effects of Invention

The present invention has excellent effects as will be described below.

(1) Since the buffer groove provided in the sealing face on thelow-pressure side of the fluid discharge means functions as a buffer forthe low-pressure fluid, which penetrates from the low-pressure fluidside onto the sealing face, against the high-pressure fluid, the timeuntil the sealing face is filled with the low-pressure fluid can bedelayed to suppress the dehydration condensation reaction of thehigh-pressure fluid.

When the low-pressure fluid is air, for example, the low-pressure sideof the sealing face can be prevented from drying with air. Theprecipitation, adhesion and accumulation of a deposition-causingsubstance through the dehydration condensation reaction of thehigh-pressure fluid can be prevented accordingly.

Even if a sudden pressure drop occurs due to a discharge of fluid by thefluid discharge means, the occurrence of cavitation can be preventedsince the sudden pressure drop is reduced by the fluid existing in thebuffer groove.

(2) The capacity of the buffer groove can be increased while securingthe sealing face by forming the buffer groove in a semicircular,rectangular or dovetail shape in cross-section, setting the width b ofthe buffer groove at 10 to 500 μm, and setting the depth h of the buffergroove at 1 to 2 times the width b.

(3) Even when a spiral groove or reverse Rayleigh step which isassociated with a potential sudden pressure drop is adopted as the fluiddischarge means, the precipitation, adhesion and accumulation of adeposition-causing substance through the dehydration condensationreaction of a high-pressure fluid can be prevented and the occurrence ofcavitation can be also prevented.

(4) Even when a fluid circulation groove, which plays a role of activelyintroducing and discharging the sealed fluid from the high-pressurefluid side onto and from the sealing face, is provided in the sealingface for preventing fluid and corrosion products and the like containedtherein from concentrating on the sealing face, is provided in additionto the spiral groove or reverse Rayleigh step, the precipitation,adhesion and accumulation of a deposition-causing substance through thedehydration condensation reaction of high-pressure fluid can beprevented and the occurrence of cavitation can be also prevented.

(5) The lubricity can be improved by broadening the space betweenrelatively sliding sealing faces by the positive pressure generatingmechanism and forming a film of fluid between the sealing faces, and thesealing performance between the sealing faces can be also improved byreleasing the positive pressure (dynamic pressure), which has beengenerated by the positive pressure generation mechanism on thehigh-pressure fluid side, to the pressure of the fluid on thehigh-pressure side through the pressure releasing groove to prevent thefluid from flowing into the fluid discharge means and the negativepressure generating capability of the fluid discharge means from beinglessened.

(6) A gentle flow of fluid is produced in the deep groove constituted bythe pressure releasing groove and the radial groove. Therefore, bubbles,impurities or the like are prevented from staying in the deep groove,fluid which is about to flow in toward the low-pressure side can besurely released to the high-pressure fluid side under a pressuregenerated by the positive pressure generating mechanism on thehigh-pressure side, and the sealing performance can be thus improved.

(7) Even when the positive pressure generating mechanism, which isprovided for improving the lubricity by broadening the space between thesealing faces and forming a film of fluid between the sealing faces, andthe pressure releasing groove, which plays a role of releasing fluid,said fluid being about to flow in toward the low-pressure side under apressure generated by the positive pressure generating mechanism on thehigh-pressure side, are provided, the precipitation, adhesion andaccumulation of a deposition-causing substance through the dehydrationcondensation reaction of high-pressure fluid can be prevented and theoccurrence of cavitation can be also prevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG.1 is a vertical cross-sectional view showing one example of amechanical seal according to a first embodiment of the presentinvention.

FIG. 2A shows a sealing face of a sliding component according to thefirst embodiment of the present invention, and FIGS. 2B to 2D are A-Across-sectional views of FIG. 2A.

FIG. 3 shows a sealing face of a sliding component according to a secondembodiment of the present invention.

FIG. 4 shows a sealing face of a sliding component according to a thirdembodiment of the present invention.

FIG. 5 shows a sealing face of a sliding component according to a fourthembodiment of the present invention.

FIG. 6 shows a sealing face of a sliding component according to a fifthembodiment of the present invention.

FIG. 7 shows a sealing face of a sliding component according to a sixthembodiment of the present invention.

FIG. 8 shows a sealing face of a sliding component according to aseventh embodiment of the present invention.

FIGS. 9A and 9B are views for explaining a positive pressure generatingmechanism composed of a Rayleigh step mechanism or the like and anegative pressure generating mechanism composed of a reverse Rayleighstep mechanism or the like, in which FIG. 9A shows the Rayleigh stepmechanism and FIG. 9B shows the reverse Rayleigh step mechanism.

FIG. 10 is a view showing a conventional technology.

DESCRIPTION OF EMBODIMENTS

Modes for carrying out the present invention will be hereinafterdescribed byway of example based on embodiments with reference to thedrawings. The dimensions, materials, shapes and relative arrangements ofcomponent parts described in the embodiments are, however, neverintended to limit the scope of the present invention only to them unlessparticularly expressly described.

{First Embodiment}

A sliding component according to a first embodiment of the presentinvention is described in reference to FIG. 1 and FIGS. 2.

In this embodiment, a description will be made taking, as an example, amechanical seal that is one example of sliding components. Although anouter circumferential side of each sliding component, which constitutesthe mechanical seal, is taken as a high-pressure fluid side (sealedfluid side) and its inner circumferential side as a low-pressure fluidside (atmospheric side) in the following description, the presentinvention is never limited thereto, and can be applied to a case inwhich the high pressure fluid side and the low pressure fluid side arereversed.

FIG. 1 is a vertical cross-sectional view showing one example of amechanical seal that is an inside mechanical seal configured to ensurethe sealing of sealed fluid on the high-pressure fluid side although thesealed fluid is apt to leak from an outer periphery of each sealing facetoward an inner periphery thereof. The mechanical seal is provided withan annular rotating ring 3 as one of the sliding components and anannular stationary ring 5 as the other sliding component. The annularrotating ring 3 is disposed on the side of a rotating shaft 1 fordriving a pump impeller (not shown) located on the high-pressure fluidside through a sleeve 2 in such a state that it is rotatable integrallywith the rotating shaft 1. The annular stationary ring 5 is disposed ina housing 4 of the pump in such a state that it is non-rotatable butmovable in an axial direction. The rotating ring 3 and stationary ring 5are slidable in close contact with each other at sealing faces Sthereof, which have been mirror-finished by lapping or the like, by acoiled wave spring 6 and a bellows spring 7, because the stationary ring5 is biased in an axial direction by the coiled wave spring 6. Thismechanical seal, therefore, prevents the sealed fluid from flowing fromthe outer periphery of the rotating shaft 1 to the atmospheric sidebetween the respective sealing faces S of the rotating ring 3 andstationary ring 5.

FIG. 2A shows a sealing face of a sliding component according toEmbodiment 1 of the present invention, which will be described taking,as an example, a case that the fluid discharge means and buffer groove,which pertain to the present invention, are formed, for example, in thesealing face S of the stationary ring 5 of FIG. 1.

The following description equally applies when the fluid discharge meansand buffer groove, which pertain to the present invention, are formed inthe sealing face S of the rotating ring 3.

In FIG. 2A, it is assumed that the outer peripheral side of the sealingface S of the stationary ring 5 corresponds to the high-pressure fluidside, the inner peripheral side corresponds to the low-pressure fluidside, for example, the atmospheric side, and the counter sealing facerotates counterclockwise.

Pumping grooves 10 as the fluid discharge means for discharging fluid tothe high-pressure fluid side by relative sliding with the countersealing face are provided in the sealing face S. The pumping grooves 10are in communication with the high-pressure fluid side, and are isolatedfrom the low-pressure fluid side by a smooth part R (which may also bereferred to as “land part R” in the present invention) of the sealingface S. The pumping grooves 10 are formed in a linear or curved shape soas to have an angle for discharging fluid to the high-pressure fluidside by relative sliding with the counter sealing face. In thisembodiment, the pumping grooves are formed in a spiral shape along therotating direction of the counter sealing face in consideration forvibrations, noises and the like.

In this description, a pumping groove of spiral shape is called a“spiral groove”, and a description will hereinafter be made about a casein which such pumping grooves are the spiral grooves 10.

A buffer groove 11 is provided in the smooth part R on the low-pressureside of the spiral grooves 10. In FIGS. 2A, the buffer groove 11 isprovided in an annular form such that it extends along the lowpressure-side ends of the spiral grooves 10.

With respect to the radial position of the buffer groove 11 in thesealing face S, the buffer groove 11 is located on the low-pressure sideof the spiral groove 10 and is isolated from the low-pressure fluid sideby the land part R.

The cross-sectional shape of the buffer groove 11 may be, for example,in a semicircular shape as shown in FIG. 2E, a rectangular shape asshown in FIG. 2C, or a dovetail groove shape as shown in FIG. 2D, but isnot limited thereto. Further, the size of the buffer groove 11 isdetermined according to the capability or the like of the spiral grooves10 as the fluid discharge means, and is set in a size having a capacitycapable of storing fluid to an extent. For example, the width b of thebuffer groove 11 may be set preferably at 10 to 500μm, more preferablyat 50 to 200 μm. The depth h of the buffer groove 11 may be setpreferably at 1 to 2 times the width b.

The buffer groove 11 has a buffering action to reduce instantaneouspenetration of low-pressure fluid to the low-pressure side of thesealing face under the fluid discharging action (sealing action) of thespiral grooves 10, and functions as a buffer for the low-pressure fluid,which penetrates from the low-pressure fluid side onto the sealing face,against the high-pressure fluid, whereby the time until the sealing faceis filled with the low-pressure fluid can be delayed to suppress thedehydration condensation reaction of the high-pressure fluid.

When the low pressure fluid is air, for example, the low-pressure sideof the sealing face can be prevented from drying with air. Theprecipitation, adhesion and accumulation of a deposition-causingsubstance through the dehydration condensation reaction of thehigh-pressure fluid can be prevented accordingly.

In the case of FIG. 2, the penetration of low-pressure fluid 12 islimited to only a small part of the sealing face on the low-pressureside under the buffer effect of the buffer groove 11, and thehigh-pressure fluid remain covering from a vicinity of the buffer groove11 to the high-pressure side.

Even if a sudden pressure drop occurs due to a discharge of fluidthrough the spiral grooves 10, the occurrence of cavitation is preventedsince the sudden pressure drop is reduced by the fluid existing in thebuffer groove 11.

{Second Embodiment}

A sliding component according to a second embodiment of the presentinvention will be described with reference to FIG. 3.

In FIG. 3, the same reference signs as those in FIG. 2 designate thesame members as in FIG. 2, and their description is omitted herein.

In a sliding component 5 shown in FIG. 3, a plurality of reverseRayleigh step mechanisms 15 as a fluid discharge means are provided in acircumferential direction in the sealing face on the high-pressure side.

Although these reverse Rayleigh step mechanisms 15 will be describedlater in detail, fluid is drawn in through grooves 15 a and reverseRayleigh steps 15 b which constitute negative pressure generatinggrooves composed of shallow grooves isolated from the high-pressurefluid side by land portions R, and the fluid is discharged to thehigh-pressure fluid side through radial grooves 15 c composed of deepgrooves communicating to the high-pressure fluid side.

A buffer groove 11 is provided in a smooth part R on the low-pressureside of the reverse Rayleigh step mechanism 15. In FIG. 3, the buffergroove 11 is provided in an annular form and apart from the reverseRayleigh step mechanism 15 toward the low-pressure fluid side.

With respect to the radial position of the buffer groove 11 in thesealing face, the buffer groove 11 is located on the low-pressure sideof the reverse Rayleigh step mechanism 15 and isolated from thelow-pressure side by the land part R.

The reverse Rayleigh step mechanisms will be described later in detail.

The cross-sectional shape, size and the like of the buffer groove 11 arethe same as in the first embodiment.

The buffer groove 11 has a buffering action to reduce the instantaneouspenetration of low-pressure fluid to the low pressure side of thesealing face under the fluid discharging action (sealing action) of thereverse Rayleigh step mechanisms 15, and functions as a buffer for thelow-pressure fluid, which penetrates from the low-pressure fluid sideonto the sealing face, against the high-pressure fluid, whereby the timeuntil the sealing face is filled with the low-pressure fluid can bedelayed to suppress the dehydration condensation reaction of thehigh-pressure fluid.

When the low-pressure fluid is air, for example, the low-pressure sideof the sealing face can be prevented from drying with air. Theprecipitation, adhesion and accumulation of a deposition-causingsubstance through the dehydration condensation reaction of thehigh-pressure fluid can be prevented accordingly.

In the case of FIG. 3, the penetration of low-pressure fluid 12 islimited to only a small part of the sealing face on the low-pressureside under the buffer effect of the buffer groove 11, and thehigh-pressure fluid remains covering from a vicinity of the buffergroove 11 to the high-pressure side.

Even if a sudden pressure drop occurs due to a discharge of fluidthrough the reverse Rayleigh step mechanisms 15, the occurrence ofcavitation is prevented since the sudden pressure drop is reduced by thefluid existing in the buffer groove 11.

{Third Embodiment}

A sliding component according to a third embodiment of the presentinvention will be described with reference to FIG. 4.

In FIG. 4, the same reference signs as those in FIG. 2 designate thesame members as in FIG. 2, and their description is omitted herein.

In FIG. 4, a plurality of fluid circulation grooves 20, as a fluidcirculating means, are provided in a circumferential direction in asealing face of a stationary ring 5. The fluid circulation grooves arein communication with the high-pressure fluid side, and are isolatedfrom the low-pressure fluid side by a land part R of the sealing face.

Each fluid circulation groove 20 is composed of an inlet portion 20 afor introducing fluid from the high-pressure fluid side, an outletportion 20 b for discharging the fluid to the low-pressure fluid sideand a communicating portion 20 c communicating the inlet portion 20 aand the outlet portion 20 b with each other in the circumferentialdirection, and is isolated from the low-pressure fluid side by the landpart R. The fluid circulation groove 20 plays a role of activelyintroducing and discharging sealed fluid from the high-pressure fluidside onto and from the sealing face for preventing the concentration offluid and corrosion products and the like contained therein on thesealing face. The inclinations of the inlet portion 20 a and outletportion 20 b are set to be large to facilitate the introduction anddischarge of sealed fluid onto and from the sealing face along therotating direction of the counter sealing face, both of them aredisposed so as to cross each other on the low-pressure fluid side (theinner peripheral side in FIG. 4), and this crossing point forms thecommunicating portion 20 c. The crossing angle between the inlet portion20 a and the outlet portion 20 b is an obtuse angle (for example, about150°).

Spiral grooves 10 for discharging fluid to the high-pressure fluid sideby relative sliding between the rotating ring 3 and the stationary ring5 are provided on the outside of parts of the sealing face of thestationary ring 5, said parts being surrounded by the fluid circulationgrooves 20, and the high-pressure fluid side, in other words, betweenthe adjacent fluid circulation grooves 20 and 20.

In the sealing face provided with the fluid circulation grooves 20, apositive pressure generating mechanisms 21 each of which includes agroove 21 a shallower than the fluid circulation grooves 20 are providedat portions enclosed by the fluid circulation groove 20 and thehigh-pressure fluid side. The positive pressure generating mechanisms 21are provided to improve the lubricity by broadening the space betweenrelatively sliding sealing faces through the generation of a positivepressure (dynamic pressure) and forming a film of fluid between thesealing faces.

Each groove 21 a is in communication with the inlet portion 20 a of thefluid circulation groove 20, and is isolated from the outlet portion 20b and the high-pressure fluid side by the land portion R.

In this embodiment, each positive pressure generating mechanism. 21 iscomposed of a Rayleigh step mechanism provided with the groove 21 a,which communicates to the inlet portion 20 a of the fluid circulationgroove 20, and a Rayleigh step 21 b, but without being limited thereto,may also be composed, for example, of a dammed femto groove, and inessence, any mechanism can be adopted insofar as it can generate apositive pressure.

The Rayleigh step mechanisms will be described later in detail.

A buffer groove 11 is provided in a smooth part R on the low-pressureside of the fluid circulation grooves 20 and spiral grooves 10. In FIG.4, the buffer groove 11 is provided in an annular form such that it isapart from the fluid circulation grooves 20 toward the low-pressurefluid side and extends along low pressure-side ends of the spiralgrooves 10.

With respect to the radial position of the buffer groove 11 in thesealing face, the buffer groove 11 is located on the low-pressure sideof the fluid circulation grooves 20 and spiral grooves 10, and isolatedfrom the low-pressure fluid side by the land part R.

The cross-sectional shape, size and the like of the buffer groove 11 arethe same as in the first embodiment.

The buffer groove 11 has a buffering action to reduce the instantaneouspenetration of low-pressure fluid to the low pressure side of thesealing face under the fluid discharging action (sealing action) of thespiral grooves 10, and functions as a buffer of the low-pressure fluid,which penetrates from the low-pressure fluid side onto the sealing face,against the high-pressure fluid, whereby the time until the sealing faceis filled with the low-pressure fluid can be delayed to suppress thedehydration condensation reaction of the high-pressure fluid.

When the low-pressure fluid is air, for example, the low-pressure sideof the sealing face can be prevented from drying with air. Theprecipitation, adhesion and accumulation of a deposition-causingsubstance through the dehydration condensation reaction of thehigh-pressure fluid can be prevented accordingly.

In the case of FIG. 4, the penetration of low-pressure fluid 12 islimited to only a small part of the sealing face on the low-pressureside under the buffer effect of the buffer groove 11, and thehigh-pressure fluid remains covering from a vicinity of the buffergroove 11 to the high-pressure side.

Even if a sudden pressure drop occurs due to a discharge of fluidthrough the spiral grooves 10, the occurrence of cavitation is preventedsince the sudden pressure drop is reduced by the fluid existing in thebuffer groove 11.

{Fourth Embodiment}

A sliding component according to a fourth embodiment of the presentinvention will be described with reference to FIG. 5.

In FIG. 5, the same reference signs as those in FIGS. 2 and 4 designatethe same members as in FIGS. 2 and 4, and their description is omittedherein.

In FIG. 5, a plurality of fluid circulation grooves 20, as a fluidcirculating means, are provided in a circumferential direction in asealing face of a stationary ring 5. The fluid circulation grooves arein communication with the high-pressure fluid side, and are isolatedfrom the low-pressure fluid side by a land part R of the sealing face.

A plurality of reverse Rayleigh step mechanisms 15 for discharging fluidto the high-pressure fluid side by relative sliding between the rotatingring 3 and the stationary ring 5 are provided in a circumferentialdirection on the outside of parts of the sealing face of the stationaryring 5, said parts being enclosed by the fluid circulation groove 20,and the high-pressure fluid side, in other words between the adjacentfluid circulation grooves 20 and 20.

In the sealing face provided with the fluid circulation grooves 20, apositive pressure generating mechanism 21 including a groove 21 ashallower than the fluid circulation grooves 20 is provided at portionsenclosed by the fluid circulation grooves 20 and the high-pressure fluidside.

A buffer groove 11 is provided in a smooth part R on a low-pressure sideof the fluid circulation grooves 20 and the reverse Rayleigh stepmechanisms 15. In FIG. 5, a buffer groove 11 is provided in an annularform and apart from the fluid circulation grooves 20 and reverseRayleigh step mechanisms 15 toward the low-pressure fluid side.

With respect to the radial position of the buffer groove 11 in thesealing face, the buffer groove 11 is located on the low-pressure sideof the fluid circulation grooves 20 and the reverse Rayleigh stepmechanisms 15 and is isolated from the low-pressure fluid side by theland part R.

The cross-sectional shape, size and the like of the buffer groove 11 arethe same as in the first embodiment.

The buffer groove 11 has a buffering action to reduce the instantaneouspenetration of low-pressure fluid to the low-pressure side of thesealing face under the fluid discharge action (sealing action) of thereverse Rayleigh step mechanisms 15, and functions as a buffer for thelow-pressure fluid, which penetrates from the low-pressure fluid sideonto the sealing face against the high-pressure fluid, whereby the timeuntil the sealing face is filled with the low-pressure fluid can bedelayed to suppress the dehydration condensation reaction of thehigh-pressure fluid.

When the low-pressure fluid is air, for example, the low-pressure sideof the sealing face can be prevented from drying with air. Theprecipitation, adhesion and accumulation of a deposition-causingsubstance through the dehydration condensation reaction of thehigh-pressure fluid can be prevented accordingly.

In the case of FIG. 3, the penetration of low-pressure fluid 12 islimited to only a small part of the sealing face on the low pressureside under by the buffer effect of the buffer groove 11, and thehigh-pressure fluid remains covering from a vicinity of the buffergroove 11 to the high-pressure side.

Even if a sudden pressure drop occurs due to a discharge of fluidthrough the spiral grooves 10, the occurrence of cavitation is preventedsince the sudden pressure drop is reduced by the fluid existing in thebuffer groove 11.

{Fifth Embodiment}

A sliding component according to a fifth embodiment of the presentinvention will be described with reference to FIG. 6.

In FIG. 6, the same reference signs as those in FIGS. 2 and 4 designatethe same members as in FIGS. 2 and 4, and their description is omittedherein.

In FIG. 6, positive pressure generating mechanisms 21, for example,Rayleigh step mechanisms which are each provided with a groove 21 a anda Rayleigh step 21 b, are provided in a sealing face on thehigh-pressure fluid side. The positive pressure generating mechanisms 21are isolated from the high-pressure fluid side and the low-pressurefluid side by land portions R, and are disposed at four equidistantpositions with equal intervals in a circumferential direction.

Spiral grooves 10 are disposed in an annular form in the sealing face onthe low-pressure fluid side of the positive pressure generatingmechanisms 21 such that they are separated from the positive pressuregenerating mechanisms 21 in a radial direction.

In addition, an annular pressure releasing groove 25 is providedcontinuously in the circumferential direction such that it is locatedbetween the spiral grooves 10 and the positive pressure generatingmechanisms 21. The pressure releasing groove 25 is separated from thegrooves 21 a of the positive pressure generating mechanisms 21 in theradial direction by the land portions R, and is connected todischarge-side ends (downstream ends) of the spiral grooves 10.

Although the positive pressure generating mechanisms 21 are provided atfour positions with equal intervals in this embodiment, at least onepositive pressure generating mechanism may suffice the need withoutbeing limited thereto.

Radial grooves 26 are provided to communicate the pressure releasinggroove 25 and the high-pressure fluid side with each other. The radialgrooves 26 are provided as many as four at equal intervals at positionswhere they are in contact with upstream ends of the groove portions 21 aof the positive pressure generating mechanisms 21 as viewed in thecircumferential direction and extend in directions orthogonal totangents of the pressure releasing groove 25. The pressure releasinggroove 25 and radial grooves 26 are deeper than the grooves 21 a of thepositive pressure generating mechanisms 21. The radial grooves 26 areformed with a width larger than that of the pressure releasing groove 25in this embodiment.

The positive pressure generating mechanisms 21 are provided to improvethe lubricity by broadening the space between relatively sliding sealingfaces through the generation of a positive pressure (dynamic pressure)and forming a film of fluid between the sealing faces.

The pressure releasing groove 25 is provided to prevent the negativepressure generating capability of the spiral grooves 10 from beinglessened due to a flow of fluid into the spiral grooves 10 on thelow-pressure side by releasing a positive pressure (dynamic pressure)generated at the positive pressure generating mechanism 21 on thehigh-pressure side to the pressure of the fluid on the high-pressureside, and plays a role of guiding the fluid, which is about to flowtoward the low-pressure side, into the pressure releasing groove 25under the pressure generated by the positive pressure generatingmechanisms 21 on the high-pressure side and releasing it to thehigh-pressure fluid side. Accordingly, the sealing performance at thesealing face can be further improved.

{Sixth Embodiment}

A sliding component according to a sixth embodiment of the presentinvention is described with reference to FIG. 7.

This embodiment has the same configurations as the fifth embodiment ofFIG. 6 except that it is different in the directions of the radialgrooves is from the fifth embodiment, and the same reference signs asthose in FIG. 6 designate the same members as in FIG. 6, and theirdescription is omitted herein.

In FIG. 7, radial grooves 27 are different in the direction. ofarrangement from the fifth embodiment although it is the same as thefifth embodiment in that they are at equal intervals as many as four atpositions where they are in contact with upstream ends of groove 21 a ofpositive pressure generating mechanisms 21.

Described specifically, the radial grooves 27 are provided such thatfour radial grooves 27 a, 27 b, 27 c, and 27 d are grouped in two pairsand that in the radial grooves 27 a and 27 b in one pair or the radialgrooves 27 c in the other pair, inlets of the radial grooves 27 a (27 c)on an upstream side, that is, on inlet sides are inclined toward theupstream side to facilitate the entry of fluid, and outlets of theradial grooves 27 b (27 d) on outlet sides are inclined toward adownstream side to facilitate the discharge of fluid.

In other words, an even number of radial grooves 27 are disposed in acircumferential direction, and are provided such that the adjacentradial grooves 27 are different from each other in the direction ofinclination, and that the inlets of the radial grooves 27 a, 27 c in theone group are inclined toward the upstream side, and the outlets of theradial grooves 27 b, 27 d in the other group are inclined toward thedownstream side.

When the radial grooves 27 are provided as described above, gentle flowsof fluid are produced in deep grooves constituted by the pressurereleasing groove 25 and the radial grooves 27. Thus, bubbles, impuritiesand the like are prevented from staying in the deep grooves, the fluidwhich is about to flow in toward the low-pressure side can be surelyreleased to the high-pressure fluid side under a generated by thepositive pressure generating mechanisms 21 on the high-pressure side,and the sealing performance can be thus improved.

Although the positive pressure generating mechanisms 21 are provided atfour positions with equal intervals in this embodiment, an even numberof positive pressure generating mechanism 21 may suffice the needwithout being limited thereto.

{Seventh Embodiment}

A sliding component according to a seventh embodiment of the presentinvention will be described with reference to FIG. 8.

This embodiment basically has the same configurations as the fifthembodiment of FIG. 6, although it is differed from the fifth embodimentin that eight pressure generating mechanisms are provided at equalintervals, and that a buffer groove is provided. The same referencesigns as those in FIG. 6 designate the same members as in FIG. 6, andtheir description is omitted herein.

In FIG. 8, spiral grooves 10 are disposed in an annular form in thesealing face at a radial center thereof, positive pressure generatingmechanisms 21, for example, Rayleigh step mechanisms are provided in thesealing face on the high-pressure fluid side of the spiral grooves 10,and a pressure releasing groove 25 is provided such that it is locatedbetween the spiral grooves 10 and the positive pressure generatingmechanisms 21. Each positive pressure generating mechanism 21 and itscorresponding pressure releasing groove 25 are in communication with thehigh-pressure fluid side through an associated radial groove 26.

The positive pressure generating mechanisms 21 are provided to improvethe lubricity by broadening the space between relatively sliding sealingfaces through the generation of a positive pressure (dynamic pressure)and forming a film of fluid between the sealing faces.

The pressure releasing groove 25 is provided to prevent the negativepressure generating capability of the spiral grooves 10 from beinglessened due to a flow of fluid into the spiral grooves 10 on the lowpressure-side by releasing a positive pressure (dynamic pressure)generated at the positive pressure generating mechanism 21 on thehigh-pressure side to the pressure of the fluid on the high-pressureside, and plays a role of guiding the fluid, which is about to flowtoward the low-pressure side, into the pressure releasing groove 25under the pressure generated by the positive pressure generatingmechanisms 21 on the high-pressure side and releasing it to thehigh-pressure fluid side.

A buffer groove 11 is provided in a smooth part R on the low-pressureside of the spiral grooves 10 as a fluid discharge means. In FIG. 8, thebuffer groove 11 is provided in an annular form such that it extendsalong low pressure-side ends of the spiral grooves 10.

With respect to the radial position of the buffer groove 11 in thesealing face, the buffer groove 11 is located on the low-pressure sideof the spiral grooves 10 and is isolated from the low-pressure fluidside by the land part R.

The cross-sectional shape, size and the like of the buffer groove 11 arethe same as in the first embodiment.

The buffer groove 11 has a buffering action to reduce the instantaneouspenetration of low-pressure fluid to the low pressure side of thesealing face under the fluid discharging action (sealing action) of thespiral grooves 10, and functions as a buffer for the low-pressure fluid,which penetrates from the low-pressure fluid side onto the sealing faceagainst the high-pressure fluid, whereby the time until the sealing faceis filled with the low pressure fluid can be delayed to suppress thedehydration condensation reaction of the high-pressure fluid.

When the low-pressure fluid is air, for example, the low-pressure sideof the sealing face can be prevented from drying with air. Theprecipitation, adhesion and accumulation of a deposition-causingsubstance through the dehydration condensation reaction of thehigh-pressure fluid can be prevented accordingly.

In the case of FIG. 3, the penetration of low-pressure fluid 12 islimited to only a small part of the sealing face on the low-pressureside under the buffer effect of the buffer groove 11, and thehigh-pressure fluid remains covering from a vicinity of the buffergroove 11 to the high-pressure side.

Even if a sudden pressure drop occurs due to a discharge of fluidthrough the spiral grooves 10, the occurrence of cavitation. isprevented since the sudden pressure drop is reduced by the fluidexisting in the buffer groove 11.

Referring next to FIGS. 9A and 9B, a description will be made about apositive pressure generating mechanism composed of a Rayleigh stepmechanism or the like and a negative pressure generating mechanismcomposed of a reverse Rayleigh step mechanism or the like.

In FIG. 9A, a rotating ring 3 and a stationary ring 5, which are opposedsliding components, undergo relative sliding as indicated by arrows. Forexample, a Rayleigh step 21 b is formed in a sealing face of thestationary ring 5 such that it is vertical to the direction of relativemovement and faces an upstream side, and a groove 21 a that is apositive pressure generating groove is formed on the upstream side ofthe Rayleigh step 21 b. The sealing faces of the opposed rotating ring 3and stationary ring 5 are flat.

When the rotating ring 3 and stationary ring 5 undergo relative movementin the directions indicated by the arrows, fluid that exists between thesealing faces of the rotating ring 3 and stationary ring 5 is about tomove following the moving direction of the rotating ring 3 or stationaryring 5 due to its viscosity. Here, a positive pressure (dynamicpressure) as shown by broken lines is generated due to the presence ofthe Rayleigh step 21.

Denoted at 20 a and 20 b are an inlet portion and an outlet portion of afluid circulation groove, respectively, R indicates a land portion, and26 is a radial groove.

Also in FIG. 9B, a rotating ring 3 and a stationary ring 5, which areopposed sliding components, undergo relative movement as indicated byarrows, a reverse Rayleigh step 15 b is formed on a sealing face of therotating ring 3 or stationary ring 5 such that it is vertical to thedirection of relative movement and faces a downstream side, and a groove15 a that is a negative pressure generating mechanism is formed on thedownstream side of the reverse Rayleigh step 15 b. The sealing faces ofthe opposed rotating ring 3 and stationary ring 5 are flat.

When the rotating ring 3 and stationary ring 5 undergo relative movementin the directions indicated by the arrows, fluid that exists between thesealing faces of the rotating ring 3 and stationary ring 5 is about tomove following the moving direction of the rotating ring 3 or stationaryring 5 due to its viscosity. Here, a negative pressure (dynamicpressure) as shown by broken lines is generated due to the presence ofthe reverse Rayleigh step 15 b.

Denoted at 15 c is a radial groove, 20 a and 20 b are an inlet portionand an outlet portion of a fluid circulation groove, respectively, and Rindicates a land portion.

Although the embodiments of the present invention have been explainedwith reference to the drawings, specific configurations are neverlimited to these embodiments, and any modifications and additions shallbe included in the present invention unless they depart from the gist ofthe present invention.

In the above-described embodiments, for example, the description wasmade about the cases in each of which the sliding component is used asone of a pair of a rotary seal ring and a stationary seal ring in amechanical seal device. However, the sliding component can be also usedas a sliding component of a bearing that is slidable toward one of axialsides of a cylindrical sealing face relative to a rotating shaft whilesealing lubricant.

In the above-described embodiments, for example, the description wasmade about the cases in each of which the high-pressure sealed fluid ispresent on the outer peripheral side. However, the sliding component canalso be applied to a case in which high-pressure fluid is present on theinner peripheral side.

In the above-described embodiments, for example, the description wasmade about the cases in each of which the spiral grooves 10 and thereverse Rayleigh step mechanisms 15 are adopted as a fluid dischargemeans. However, the fluid discharge means may comprise dimples withoutbeing limited to such cases.

In the above-described cases, for example, the description was madeabout the cases in each of which the buffer groove 11 is formedcontinuously in an annular form. However it does not have to be formedcontinuously and may be formed in an intermittent form. In essence, thebuffer groove 11 may be formed in any form insofar as it has a capacityequipped with buffering action.

REFERENCE SIGNS LIST

1 Rotating shaft

2 Sleeve

3 Rotating ring

4 Housing

5 Stationary ring

6 Coiled wave spring

7 Bellows

10 Pumping groove (Spiral groove)

11 Buffer groove

12 Low-pressure fluid

15 Reverse Rayleigh step mechanism

15 a Groove

15 b Reverse Rayleigh step (Negative pressure generating mechanism)

15 c Radial groove

20 Fluid circulation groove

20 a Inlet portion

20 b Outlet portion

20 c Communicating portion

21 Rayleigh step (Positive pressure generating mechanism)

21 a Groove

21 b Rayleigh step

25 Pressure releasing groove

26 Radial groove

27 Radial groove

S Sealing face

R Land part or portion

The invention claimed is:
 1. A pair of sliding components provided, on ahigh-pressure side of one of relatively sliding sealing faces thereof,with a fluid discharge comprising a plurality of spiral grooves eachhaving a spiral direction that causes fluid to discharge to ahigh-pressure fluid side, each of the spiral grooves being incommunication with high-pressure fluid side, wherein a buffer groove forreducing penetration of low-pressure fluid toward the high-pressurefluid side is provided in the sealing face on a low-pressure side of thespiral grooves and communicates with low-pressure-side end of each ofthe spiral grooves.
 2. The sliding components according to claim 1,wherein the sealing face is provided, on the high-pressure side, with aplurality of fluid circulation grooves in communication with thehigh-pressure fluid side in addition to the spiral grooves, wherein eachof the spiral grooves is arranged between adjoining two of the fluidcirculation grooves on outside of a space enclosed by each of the fluidcirculation grooves and the high-pressure fluid side, and wherein aplurality of positive pressure generating mechanisms are each providedin the space enclosed by each of the fluid circulation grooves and thehigh-pressure fluid side.
 3. The sliding components according to claim2, wherein each of the positive pressure generating mechanisms includesa groove with a Rayleigh step, the groove of each of the positivepressure generating mechanisms communicating with an inlet portion ofeach of the fluid circulation grooves and being isolated by a landportion from an outlet portion of each of the fluid circulation groovesand the high-pressure fluid side.
 4. The sliding components according toclaim 1, wherein the sealing face is provided, on the high-pressure sideof the spiral grooves, with a plurality of positive pressure generatingmechanisms.
 5. The sliding components according to claim 4, wherein eachof the positive pressure generating mechanisms includes a groove with aRayleigh step, the groove of each of the positive pressure generatingmechanisms being isolated from the high-pressure fluid side by a landportion.
 6. The sliding components according to claim 5, wherein thesealing face is provided with a pressure releasing groove of annularform, and with a radial groove causing the pressure releasing groove tocommunicate with the high-pressure fluid side.
 7. A pair of slidingcomponents provided, on a high-pressure side of one of relativelysliding sealing faces thereof, with a fluid discharge comprising aplurality of spiral grooves for discharging fluid to a high-pressurefluid side, each of the spiral grooves being in communication withhigh-pressure fluid side, wherein a buffer groove for reducingpenetration of low-pressure fluid toward the high-pressure fluid side isprovided in the sealing face on a low-pressure side of the spiralgrooves so as to extend along low-pressure-side ends of the spiralgrooves, wherein the sealing face is provided, on the high-pressure sideof the spiral grooves, with a plurality of positive pressure generatingmechanisms, wherein each of the positive pressure generating mechanismsincludes a groove with a Rayleigh step, the groove of each of thepositive pressure generating mechanisms being isolated from thehigh-pressure fluid side by a land portion, and wherein the sealing faceis provided with a pressure releasing groove of annular form, and with aradial groove causing the pressure releasing groove to communicate withthe high-pressure fluid side.
 8. The sliding components according toclaim 7, wherein the plurality of positive pressure generatingmechanisms comprise a plurality of fluid circulation grooves incommunication with the high-pressure fluid side in addition to thespiral grooves, wherein each of the spiral grooves is arranged betweenadjoining two of the fluid circulation grooves on outside of a spaceenclosed by each of the fluid circulation grooves and the high-pressurefluid side, and wherein a plurality of positive pressure generatingmechanisms are each provided in the space enclosed by each of the fluidcirculation grooves and the high-pressure fluid side.
 9. The slidingcomponents according to claim 8, wherein the groove of each of thepositive pressure generating mechanisms communicating with the inletportion of each of the fluid circulation grooves is isolated by the landportion from an outlet portion of each of the fluid circulation groovesand the high-pressure fluid side.